Resin trap device for use in ultrapure water systems and method of purifying water using same

ABSTRACT

The present invention is directed to the use of a resin trap device to remove large resin particles from water in a water purification system to thereby protect downstream ultrafiltration equipment. The present invention includes a resin trap device which comprises a housing and a resin strainer disposed within the housing. The resin strainer includes a plurality of openings having a particle pass size of between about 100 μm and about 250 μm, and thus allows water and small particles to pass through the resin trap device and large particles to be retained in the resin trap device. The present invention also includes a water purification system including a water source, a resin bed and the resin trap device, and a method of purifying water using the resin trap device of the invention.

FIELD OF THE INVENTION

The invention relates to the use of ion-complexing resin beds in waterpurification systems, and more particularly, to a resin trap device forremoving resin particles in ultrafiltration systems.

BACKGROUND OF THE INVENTION

The production of ultrapure water is essential to the fabrication ofdefect-free silicon chips in the microelectronics industry. Typically,producing ultrapure water involves treating water through a number ofprocesses to remove ion contaminants. In particular, the ultrapure water(also known as deionized or high filtered water) must be virtually freeof ionic contaminants, typically bringing the specific resistivity togreater than or equal to about 18.2 M·ohm·cm at 20° C.

In these water purification systems, water is initially treated by aseries of steps which control the pH level of the intake water, addchlorine to control bacteria growth in the water, remove particulatematter, remove added chlorine so that it does not damage delicatedownstream equipment, and warm the water to about 21° C. (70° F.). Afterthese initial treatment steps, the water is typically deionized in areverse osmosis process and then degassed. The water is then furtherdeionized by a first set of resin beds. The resin beds include beads ofan ion-complexing resin which are retained in the resin beds by a screenon the exit header pipes and laterals inside the bed. The water passesthrough the resin beds so that it intimately contacts the resin beads toremove ion contaminants from the water. The water then passes through aplurality of 1.0 μm particle pass size microfiltration modules ormicrofilters to remove resin particles which may have escaped the resinbeds and entered the water purification system. These microfilterscontain membranes of spun polypropylene or nylon which are housed in astainless steel housing and arranged so that water enters the outerlumens of each microfilter and permeates to a common inner plenum withinthe housing. The water passes through the microfilters to an ultravioletsterilization unit to control bacterial contamination and is typicallystored as deionized water.

The deionized water from storage is then treated by a second set ofwater purification steps. These water purification steps includeultraviolet sterilization to control bacterial contamination and toconvert organic materials to low molecular weight charged ions, andpolishing reverse osmosis for the removal of charged ions andparticulate matter. The water then passes through a final polishingsystem which includes another ultraviolet sterilizer and a second set ofion-complexing resin beds to remove ion contaminants from the water.Another set of microfilters is positioned downstream from the second setof resin beds to remove resin particles which may escape from the resinbeds. These microfilters also have a small particle pass size (e.g. 1 μmabsolute and 0.1 μm or 0.2 μm nominal rated) and include apolyvinylidene fluoride (PVDF) lined stainless steel housing to avoidparts per trillion metals contamination. Immediately after passingthrough these microfilters, the water advances to a set of cross-flowultrafilters that remove additional ion contaminants and very smallparticles to produce ultrapure water.

One problem that occurs in these water purification processes is thatresin particles escape the ion-complexing beds and become entrained inthe water flow. This “fouling” of the water occurs, to some degree,during normal system operation of the purification system. However,events such as the breakage of exit flow strainers in the resin beds cancause a sudden large release of resin particles into the flow of water.This sudden release of resin particles can blind downstream microfiltersand ultrafilters and clog system apertures and instrumentation therebyreducing or stopping the flow of water in the ultrafiltration process.

As mentioned above, the conventional method of removing resin particlesfrom the water purification system prior to ultrafiltration is to use aplurality of microfilters having a maximum particle pass size of between0.1 and 1 μm. Unfortunately, because of the small particle pass size ofthese microfilters, the high pressure drop through these microfilterssignificantly decreases the flow rate of the water through the waterpurification system. Therefore, ultrapure water often cannot be producedat the flow rates desired for manufacturing processes.

An additional problem associated with these microfilters is that it canbe difficult to remove the resin particles trapped in the microfilters.In particular, these microfilters cannot be flushed and thus resinparticles accumulate in the microfilters.

As a result, this accumulation makes it necessary to replace themicrofilters in the water purification system on an annual or biannualbasis. In particular, if these microfilters are not replaced, the watercan become more readily contaminated and resin particles are more likelyto be released into the water purification system. The replacement ofmicrofilters causes great expense to the operation of the waterpurification system not only because the microfilters are expensive butbecause their replacement also requires that the entire purificationsystem be shut down and opened to the atmosphere.

There is therefore a need in the art of ultrapure water systems for anapparatus and method to remove potentially damaging resin particles fromthe flow of water that does not cause an undesirable pressure drop, isnot subject to contamination and is suitable for continuous operationand cleansing by flushing with water.

SUMMARY OF THE INVENTION

The present invention is a resin trap device and method of using same toremove large resin particles from the water in a water purificationsystem. In particular, the resin trap device removes large resinparticles to protect downstream ultrafiltration equipment from damageeven when large releases of resin particles enter the purificationsystem such as by breakage of the resin bed exit flow strainer in thesystem. The resin trap device of the invention does not cause anundesirable pressure drop in the water flow thereby allowing ultrapurewater to be produced at good flow rates. In addition, the resin trapdevice can be cleansed by flushing with water or disassembly to removeresin particles and thus limit contamination of the water and the needto replace filtration apparatus on an annual or biannual basis.

In accordance with the present invention, it has been discovered that itis not necessary to remove resin particles down to micron size prior tothe ultrafiltration of water. In particular, it has been discovered thata light flow of small particles having an average diameter of less thanabout 150 μm (6 mils) generally does not harm the ultrafiltrationequipment and these small particles can be harmlessly diverted into areject water stream and tapped out of the ultrafiltration system. Largeresin particles having an average diameter of greater than about 150 μm,on the other hand, can harm the cross-flow ultrafiltration membranesfound in the final cross-flow ultrafilters and can also harm otherdelicate equipment located downstream from the resin beds. Therefore, ithas been determined that damage to the ultrafilters can be avoided byremoving the large resin particles from the water purification system.

The present invention comprises a resin trap device for removing largeresin particles from a water purification system. The resin trap devicecomprises a housing and one or more resin strainers disposed within thehousing. Each resin strainer includes a plurality of openings having aparticle pass size of between about 100 μm (4 mils) and about 250 μm (10mils) thereby allowing water and particles having a particle size ofless than the particle pass size to flow through the openings but notallowing particles having a particle size of greater than the particlepass size to flow through the openings. Preferably, the particle passsize is between about 125 μm (5 mils) and about 175 μm (7 mils), andmore preferably, about 150 μm. By using resin strainers having theseparticle pass sizes, the majority, if not all, of the large resinparticles can be removed while still maintaining a minimal pressure dropacross the resin trap device. As a result, ultrapure water can beproduced at good flow rates and delivered at these rates to specific enduses.

The resin trap device of the invention can be included in a waterpurification system which comprises a source of water, a resin bed, andthe resin trap device. The resin bed comprises an inlet for receivingwater from the water source, a plurality of resin particles forintimately contacting the water and removing ions from the water, and anoutlet. The resin trap device is external to the resin bed and in fluidcommunication with the outlet of the resin bed. In accordance with theinvention, water and any particles entrained therein flow from the resinbeds into the resin trap device and large particles having a diameter ofgreater than the particle pass size of the openings are retained in theresin trap device to prevent damage to downstream ultrafiltrationequipment. Water and small particles having a diameter of less than theparticle pass size of the openings flow through the openings, exit theresin trap device, and further advance to the ultrafiltration system.The small particles that enter the ultrafilters in the ultrafiltrationsystem can then be easily diverted into a reject water stream andremoved from the ultrafiltration system. The resulting filtrate from theultrafiltration system is suitable for ultrapure water applications.

The present invention also includes a method of purifying and filteringwater to produce water suitable for ultrafiltration. First, water ispassed through a resin bed and intimately contacted with resin particlesto remove ions from the water and thereby purify the water. The purifiedwater that exits the resin bed is then advanced from the resin bed intoa resin trap device comprising a housing and a resin strainer disposedwithin the housing. The resin strainer contains a plurality of openingshaving a predetermined particle pass size as described above and retainslarge particles having a diameter of greater than the particle pass sizeand allows water and small particles having a diameter of less than theparticle pass size to flow through the resin trap device.

In one preferred embodiment of the invention, water is advanced from theresin bed directly into the housing, large particles are retained in thehousing, and water and small particles are allowed to flow from thehousing into the resin strainer and out of the resin trap device. Inthis embodiment, a fluid inlet in said housing is in fluid communicationwith the outlet of the resin bed and the resin strainer comprises anoutlet. The water from the outlet of the resin bed enters through thefluid inlet in the housing, water and small particles pass through theopenings in the resin strainer to an outlet of the resin strainer, thewater and small particles exit the resin trap device through an outletin the resin strainer, and the large particles are retained in thehousing by the resin strainer.

In another preferred embodiment of the invention, water is advanced fromthe resin bed directly into the resin strainer, large particles areretained in the resin strainer, and water and small particles areallowed to flow from the resin strainer into the housing and out of theresin trap device. In this embodiment, the resin strainer furthercomprises an inlet in fluid communication with the outlet of the resinbed. The water from the outlet of the resin bed enters through the inletof the resin strainer, the water and small particles pass through theopenings into the housing, the water and small particles exit thehousing through the outlet in the housing, and large particles areretained in the resin strainer.

In yet another preferred embodiment of the invention, the resin trapdevice comprises a housing including a fluid inlet for receiving a flowof water, a plurality of spherical resin strainers disposed within thehousing, and a primary outlet in fluid communication with each of theresin strainers to allow the flow of water out of the resin trap device.The resin strainers each include a plurality of openings having apredetermined particle pass size as described above so that water entersthe resin trap device through the inlet of the housing, water and smallparticles having a diameter of less than the particle pass size flowfrom the housing into the resin strainers through the openings and outof the resin trap device through the primary outlet, and large particleshaving a diameter of greater than the particle pass size are retained inthe housing. The resin trap device can further include a plurality ofsecondary fluid outlets, each of which corresponds to a resin strainerand is in fluid communication with the primary outlet so that water andsmall particles flow from the resin strainers through the secondaryoutlets into the primary outlet and out of the resin trap device.

The resin trap device can be easily cleaned by flushing water throughthe resin trap device to force particles retained in the resin trapdevice into an auxiliary drain line. Typically, a valve attached to anoutlet of the housing or the resin strainer is manipulated to providewater to clean the resin trap device. Alternatively, the resin trapdevice can be cleaned by isolation, removal and disassembly of the resintrap device. In either case, multiple resin trap devices are preferablyprovided in a parallel flow configuration to ensure continuous operationeven during cleaning of one or more of the resin trap devices.

These and other features and advantages of the present invention willbecome more readily apparent to those skilled in the art uponconsideration of the following detailed description and accompanyingdrawings which describe both the preferred and alternative embodimentsof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a water purification systemincluding a resin trap device according to the present invention.

FIG. 2 is a side cutaway view of an embodiment of a resin trap deviceaccording to the present invention.

FIG. 3 is a side cutaway view of another embodiment of a resin trapdevice according to the present invention.

FIG. 4 is a cross-sectional view of the resin trap device of FIG. 3taken along line 4—4 of FIG. 3.

FIG. 5 is a side cutaway view of yet another embodiment of a resin trapdevice according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings and the following detailed description, preferredembodiments are described in detail to enable practice of the invention.Although the invention is described with reference to these specificpreferred embodiments, it will be understood that the invention is notlimited to these preferred embodiments. But to the contrary, theinvention includes numerous alternatives, modifications and equivalentsas will become apparent from consideration of the following detaileddescription and accompanying drawings. In the drawings, like numbersrefer to like elements throughout.

FIG. 1 illustrates a preferred water purification system 10 for use inthe invention. In accordance with the invention, water is initiallytreated by a series of initial treatment units indicated generally at12. These units 12 can be used to control the pH level of the intakewater, to add chlorine to control bacterial growth in the water, toremove particulate matter such as silica particles, to remove addedchlorine so that it does not damage delicate downstream equipment, andto warm the water to about 21° C. (70° F.). The water can then besubjected to reverse osmosis treatment, degasification, primarydeionization and filtration, and ultraviolet radiation treatment. Afterthis initial treatment, the water can be stored in a deionized waterstorage tank 13. The water from the tank 13 is then advanced to anultraviolet sterilizer 14 to reduce the total oxidizable carbon (TOC)content by breaking down organic contamination into lower molecularweight organic charged ions. The water from the sterilizer 14 is thenadvanced to a reverse osmosis system 15 for deionization and then to asecond ultraviolet sterilizer 16 for treatment and removal of bacterialcontamination.

The water exiting the ultraviolet sterilizer 16 is then furtherdeionized by passing the water through a set of resin beds 17 arrangedparallel to one another. An exemplary resin bed 17 is illustrated inFIG. 2. The water enters the resin beds 17 through an inlet 18. As shownin the cutaway portion of the resin bed 17 in FIG. 2, the resin bedsinclude a mixture of beads 19 of ion-complexing resins, e.g., strongacid cation, strong base anion, and inert resins. These beads 19 areretained in the resin bed 17 by an exit flow strainer 20 which isconnected to the outlet line 21 by a threaded connection 22. Duringoperation, water passes through the inlet 18 into the resin bed 17,intimately contacts the resin beads 19, and flows through the strainer20 and out of the resin beds through an outlet line 21. The inlet line18 and outlet line 21 also include isolation valves 24 and 26 whichallow the resin bed 17 to be disconnected from the water purificationsystem for service (e.g. replacement of the strainer 20) and cleaning.

The exit flow strainer 20 in the resin bed 17 is designed to preventlarge resin particles from flowing into the outlet line 21.Nevertheless, although the exit flow strainer 20 prevents most of thelarge resin particles from flowing into the outlet line 21, the straineris subject to breakage which causes a large release of resin particles.In addition, resin particles often enter the outlet line 21 through thethreaded connection 22. As described above, large resin particles candamage downstream equipment, most notably, the ultrafiltrationequipment.

In the present invention, a resin trap device is located in fluidcommunication with and downstream from the resin beds 17, and is used inplace of conventional microfilters in the water purification system 10.As shown in phantom in FIG. 1, a resin trap device 30 can be included inthe outlet line 21 of the resin bed 17 or a resin trap device 100 can belocated further downstream in the water purification system 10. As shownin FIG. 1, more than one resin trap device is preferably provided inparallel to allow continuous operation of the water purification system10 even during cleaning of the resin trap devices. For example, for theresin trap devices 30 illustrated in FIG. 1, more than one resin bed 17is provided in parallel, each with a corresponding resin trap device 30.Alternatively, the resin trap devices 100 illustrated in FIG. 1 areprovided as separate units in parallel. The resin trap devices used inaccordance with the invention remove large particles from the waterpurification system thereby limiting damage to downstream equipment suchas the ultrafiltration equipment in ultrafiltration system 42. The waterand entrained small particles that exit the resin trap device furtheradvance to the ultrafiltration system 42. The ultrafiltration system 42comprises one or more ultrafilters 44, typically in parallel, and waterenters the ultrafilters by inlets 45. The water that exits theultrafilters 44 is ultrapure and preferably has a specific resistivityof greater than or equal to 18 M·ohm·cm at 20° C. In addition, any smallparticles that enter the ultrafilters 44 are typically harmlesslysloughed off the ultrafiltration membranes in the ultrafilters and intoa reject water stream 46 that flows out of ultrafiltration system 42into a drain 48 or to other less critical uses. The ultrapure water canflow to a specific point of use 50 and then either be sent to a drainline 52 or recycled to the storage unit 13.

FIG. 2 illustrates one embodiment of the invention wherein the resintrap device 30 is included in the outlet line 21 of the resin bed 17. InFIG. 2, the resin trap device 30 is installed in the outlet line 21using a pair of threaded connections 54 and 56. However, althoughthreaded connections 54 and 56 are illustrated, union or flangedconnections can also be used. In accordance with the invention, theresin trap device 30 comprises a housing 32 and at least one resinstrainer 34 disposed within the housing. The resin strainer 34 can begenerally spherical, generally cylindrical or any other suitable shape.The housing 32 corresponds to the shape of the resin strainer 34 and isgenerally cylindrical. In the embodiment illustrated in FIG. 2, theresin strainer 34 is generally spherical and the housing 32 is generallycylindrical. In the embodiment of FIG. 2, the housing 32 is heldtogether by a threaded connection 35 to allow easy disassembly but canbe held together by alternative means. In addition, as illustrated inFIG. 2, the resin strainer 34 is preferably connected to the housing bya threaded connection 36 to allow easy removal of the resin strainer.

According to the invention, the resin strainer 34 comprises a pluralityof openings 38 having a particle pass size of between about 100 μm andabout 250 μm. Preferably, the particle pass size is between about 125 μmand about 175 μm, more preferably about 150 μm. The term “particle passsize” as used herein describes the maximum particle size which can passthrough the openings 38 of the resin strainer 34, i.e., openings havinga 150 μm particle pass size have dimensions such that particles having adiameter of less than 150 μm can pass through the openings and particleshaving a diameter of greater than 150 μm cannot pass through theopenings. In the embodiment illustrated in FIG. 2, the openings 38 aregenerally vertical but can be generally horizontal or any otherorientation which allows retention of the large particles without asignificant pressure drop across the resin trap device 30.

For use in the water purification system 10, the resin strainer 34 andat least an inner surface of the housing 32 are preferably constructedof an inert polymer material to prevent contamination of the water inthe resin trap device 30. In addition, the piping of the waterpurification system 10 is preferably formed of an inert polymermaterial. Preferably, the inert polymeric material is a fluorinatedpolymer such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene(PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA)polymers, polychlorotrifluoroethylene (PCFE), ethylenetetrafluoroethylene (ETFE), and ethylene chlorotrifluoroethylene(ECTFE). More preferably, the fluorinated polymer is PVDF. The remainderof the housing 32 can be formed of a fluorinated polymer or any othersuitable material such as stainless steel. Preferably, for theembodiment of FIG. 2, the entire housing 32 is formed of a translucentinert polymer material such as PVDF.

In operation of the embodiment of FIG. 2, water flows into the resin bed17 through inlet line 18 where the water intimately contacts a pluralityof ion-complexing resin beads 19. The water then flows into the outletline 21 of the resin bed 17 through a exit flow strainer 20. The waterand any particles which escape the exit flow strainer 20 flow from theoutlet line 21 into the housing 32. The water and particles smaller thanthe particle pass size of the openings 38 flow into the resin strainer34 and out of the resin trap device 30 through an outlet 40. The largeparticles having a diameter greater than the particle pass size, on theother hand, are retained in the housing 32.

The resin trap device 30 of FIG. 2 can be easily removed and cleaned toremove particles retained in the housing 32. In accordance with theinvention, pressure indicators (not shown) can be located in the outletline 21 (or resin trap device inlet) and outlet line 40. A highdifferential in pressure between these pressure indicators, e.g.,greater than 2 psi, or visual presence of resin particles as observedthrough the translucent walls of the housing 32 can be used to indicatea need to clean the resin trap device 30. In order to clean the resintrap device 30, the threaded connections 54 and 56 can be disconnectedto remove the resin trap device from the outlet line 21. Typically, thisis accomplished by closing a valve 58 in the outlet 40 and the valve 26and disconnecting the threaded connections 54 and 56. Once removed fromthe outlet line 21, the housing 32 of the resin trap device 30 can beopened by disconnecting the threaded connection 35 to remove anyretained particles from the housing or to replace the resin strainer 34if desired. The resin trap device 30 can then be easily reassembled andreinstalled for use in the invention.

FIGS. 3 and 4 illustrate one embodiment of the resin trap device 100.The resin trap device 100 includes a generally cylindrical housing 102and a cylindrical resin strainer 104 concentrically disposed within thehousing. The resin strainer 104 includes a plurality of openings 106having a particle pass size of between about 100 μm and about 250 μm,preferably between about 125 μm and about 175 μm, and more preferablyabout 150 μm. In the embodiment shown in FIG. 2, the openings 106 in theresin strainer 104 are horizontal slots but can be vertical slots orhave any other orientation in accordance with the invention. Thematerials used in the resin trap device are as described above with theresin strainer 104 and inner surface 152 of the housing 102 beingpreferably formed of an inert polymer material and the remainder of thehousing being formed either of an inert polymer material or stainlesssteel.

During operation of the resin trap device 100 of FIGS. 3 and 4, waterflows into the resin trap device through inlet 108 which is in fluidcommunication with the resin strainer 104. Water and small resinparticles flow through the openings 106 and into the housing 102 and outof the resin trap device 100 through an outlet 110. As illustrated inFIG. 2, the outlet 110 has an axis that is perpendicular to the axis ofinlet 108 but the axis of the outlet 110 can be oriented in otherrelationships with the axis of the inlet (e.g. collinear or parallel).The large particles having a diameter of greater than the particle passsize cannot flow through openings 106 and are trapped in the resinstrainer 104 thereby limiting damage to downstream ultrafiltrationequipment.

The resin strainer 104 and the housing communicate at a discharge end112 with a valve 113 such as a ball or diaphragm valve. The valve 113 isclosed during normal operation of the resin trap device 100 but can beopened to permit flushing of the resin strainer 104 to remove retainedresin particles. In particular, when the accumulation of large resinparticles in the resin strainer 104 causes an undesirable pressure dropacross the resin trap device 100 as measured by pressure indicators (notshown) in the inlet 108 and outlet 110, the resin strainer 104 can beflushed by opening the valve 113 and flowing water through the resinstrainer and out through an auxiliary line 160.

The resin strainer 104 is retained in the resin trap device 100 in thearea of the inlet 108 by an apertured flange 114 that is compressed andretained by a pair of housing flange adapters 116. A pair of ringgaskets 118 are interposed between flange 114 and adapters 116 to form awatertight seal. A first pair of first apertured flange rings 120 areretained and compressed about adapters 116 by a first set of fasteners122 such as bolts which extend through the apertures of flange 114 and apair of securing means 123 such as nuts secure the fasteners. At thedischarge end 112, housing 102 is sealingly joined to the resin strainer104 by a second pair of apertured flange rings 132, a first singleO-ring 134, a second single O-ring 136, a single housing flange adapter138 and a second set of bolts 140 and nuts 141.

In one embodiment, the resin strainer 104 is 1.2 meters long andcomprises an elongate cylindrical section 142 having an inner diameterof 81.4 mm and an outer diameter of 90.0 mm. The resin strainer 104 hasa neck 146 that is sealingly mated with valve 113. The resin strainer104 can be made of cylindrical sections that are infrared butt fusionwelded together at a set of weld points 148. The housing 102 in theresin trap device 100 preferably has an inner diameter of 99.2 mm and anouter diameter of 110 mm. The slots 106 are preferably 31.8 mm long,about 150 microns wide, and are spaced apart by 3.2 mm into a set ofgroups 150 of 46 slots. Groups 150 are spaced apart by a set of 12.7 mmgaps 152.

FIG. 5 shows an alternative preferred embodiment of a resin trap device200 according to the invention that can be used in place of the resintrap device 100. The resin trap device 200 includes a cylindricalhousing 202 and a plurality of spherical resin strainers 204 disposedwithin the housing. The materials used in the housing 202 and resinstrainers 204 are preferably the same as those described for theembodiment of FIGS. 3 and 4. The resin strainers 204 each contain aplurality of openings 206 having a particle pass size such as describedabove. As shown in FIG. 5, the openings 206 are horizontally orientedbut can be oriented differently as described above. The resin trapdevice 200 also includes a primary outlet 210 and a plurality ofsecondary outlets 215 which are in fluid communication with then resinstrainers 204 and the outlet 210. The number of secondary outlets 215 isthe same as the number of resin strainers 204 and each secondary outletis matched with a resin strainer. The resin strainers 204, primaryoutlet 210 and secondary outlets 213 form a manifold assembly 240 whichhas been found particularly useful for use in the invention. Themanifold assembly 240 is sealingly fitted into the resin trap device 200through end wall 270 of housing 202. Specifically, the manifold 240 isretained in the end wall 270 by a pair of apertured flange rings 214.The flange rings 214 are retained and compressed about a gasket 216 by afirst set of fasteners 218 such as bolts which extend through theapertures of flange 214 and a pair of securing means 219 such as nutssecure the fasteners.

In operation of the resin trap device of FIG. 5, water enters the resintrap device 200 through an inlet 208 which is in fluid communicationwith the housing 202 and flows into the housing. Water and small resinparticles then flow into the resin strainers 204 through openings 206into the secondary outlets 215 and out of the resin trap device 200through primary outlet 210. When the large resin particles accumulate inthe housing 202 and cause a corresponding undesirable pressure dropacross the resin trap device 200 as measured by pressure indicators (notshown) in the inlet 208 and outlet 210, the housing can be flushed byopening the valve 213 and flowing water through the inlet 208 and intothe housing and forcing resin particles out of the resin trap devicethrough an auxiliary line 220.

As will be readily understood by those skilled in the art, the presentinvention represents a new paradigm in water purification andultrafiltration systems. In particular, rather than removing resinparticles down to the micron size, only the larger particles which aremore likely to damage the downstream ultrafiltration equipment areremoved from the water purification system. Therefore, the resin trapdevice of the invention does not cause an undesirable pressure drop inthe water flow thereby allowing ultrapure water to be produced at goodflow rates. For example, the resin trap device 200 of FIG. 5 hasdemonstrated a pressure drop of only 0.5 psig at a flow rate of 61 gpm(gallons per minute) as compared to pressure drops of 8 to 14 psig atflow rates of 50 to 85 gpm across conventional microfilters. As aresult, water purification systems in accordance with the invention canmore easily meet capacity demands and have sufficient pressure to beused in spray nozzles and with other end use equipment.

In addition to helping to produce ultrapure water at good flow rates,the resin trap device can also be easily cleansed by flushing ordisassembly to remove resin particles and thus limit contamination ofthe water. Moreover, the resin trap device of the invention does notneed to be replaced on an annual or biannual basis thus reducingoperating costs, minimizing downtime, and eliminating potentialcontamination from obtrusive entry into the water purification system.Because the resin trap device can be formed completely of fluorinatedpolymer and does not have to be formed of a fluorinated polymer linedstainless steel, the resin trap device also is not subject to thecontamination that can occur when the liner is damaged. Furthermore, theresin trap device of the invention can be sterilized by ozonation,peroxide, hot water, or other standard ultrapure water sterilizationmethods.

It is understood that upon reading the above description of the presentinvention and reviewing the accompanying drawings, one skilled in theart could make changes and variations therefrom. These changes andvariations are included in the spirit and scope of the followingappended claims.

That which is claimed:
 1. A purification system for the production ofultrapure water comprising: a source of water; a resin bed comprising aninlet for receiving water from said source, a plurality of resinparticles for intimately contacting the water and removing ions from thewater, and an outlet; and a resin trap device external to said resin bedand in fluid communication with the outlet of the resin bed comprising:a housing, and a resin strainer disposed within said housing, saidstrainer including a plurality of openings having a particle pass sizeof between about 100 μm and about 250 μm, whereby water from the outletof said resin bed enters said resin trap device, water and smallparticles having a diameter of less than the particle pass size flowthrough said openings and flow out of said resin trap device, and largeparticles having a diameter of greater than the particle pass size areretained in the resin trap device; and an ultrafilter downstream fromsaid resin trap device for filtering the water to produce ultrapurewater having a specific resistivity of greater than or equal to 18M·ohm·cm at 20° C.; wherein said water purification system is free ofmicrofilters having a maximum particle pass size of between 0.1 μm and 1μm downstream from said resin bed and upstream from said ultrafilter. 2.The water purification system according to claim 1 wherein the openingsof said resin strainer have a particle pass size of between about 125 μmand 175 μm.
 3. The water purification system according to claim 1wherein said housing further comprises a fluid inlet in fluidcommunication with the outlet of the resin bed and said resin strainerfurther comprises an outlet, whereby the water from the outlet of saidresin bed enters through the fluid inlet in said housing, water andsmall particles pass through said openings in said resin strainer to theoutlet of said resin strainer, the water and small particles exit theresin trap device through the outlet in said resin strainer, and thelarge particles are retained in the housing.
 4. The water purificationsystem according to claim 1 wherein said housing further comprises anoutlet and said resin strainer further comprises an inlet in fluidcommunication with the outlet of said resin bed, whereby the water fromthe outlet of said resin bed enters through the inlet of said resinstrainer, the water and small particles pass through said openings intosaid housing, the water and small particles exit the housing through theoutlet in said housing, and large particles are retained in the resinstrainer.
 5. The water purification system according to claim 1 whereinthe resin strainer in said resin trap device is generally spherical. 6.The water purification system according to claim 1 wherein each of thehousing and the resin strainer in said resin trap device are generallycylindrical and the resin strainer is concentrically disposed inside thehousing.
 7. The water purification system according to claim 1 whereinsaid resin trap device comprises a plurality of resin strainers, each ofsaid strainers having plurality of openings, said openings having aparticle pass size of between about 100 μm and about 250 μm.
 8. Thewater purification system according to claim 1 wherein the inlet of saidhousing is in fluid communication with the outlet of said resin bed andsaid resin trap device further comprises a primary outlet and aplurality of spherical strainers within the housing, each of saidstrainers in fluid communication with the primary outlet of said resintrap device and comprising a plurality of openings, said openings havinga particle pass size of between about 100 μm and about 250 μm.
 9. Thewater purification system according to claim 1 wherein the openings insaid resin strainer are in the form of horizontal slots.
 10. The waterpurification system according to claim 1 wherein the openings in saidresin strainer are in the form of vertical slots.
 11. The waterpurification system according to claim 1 including a valve incommunication with said resin trap device to permit the flushing ofwater through said resin trap device.
 12. The water purification systemaccording to claim 1 wherein the resin strainer and an inner surface ofthe housing are formed of a inert polymeric material.
 13. The waterpurification system according to claim 12 wherein said inert polymericmaterial is a fluorinated polymer.
 14. The water purification systemaccording to claim 13 wherein said fluorinated polymer is polyvinylidenefluoride.